JP6204714B2 - Densitometer and concentration measurement method - Google Patents

Description

  The present invention relates to a densitometer and a density measuring method using the densitometer, and more particularly to a densitometer capable of temperature correction and a density measuring method.

  The concentration of a volatile measurement target substance (for example, alcohol) in a sample solution is calculated from the gas concentration of the measurement target substance in the gas when the specific gas is bubbled at a predetermined temperature (measurement temperature) and the measurement temperature. Can be obtained.

  Therefore, conventionally, a predetermined gas concentration is obtained in the carrier gas at a strictly controlled constant temperature, and the concentration is calculated based on the gas concentration.

  That is, as shown in FIG. 6, water from a thermostat (not shown) is circulated in a thermostatic container 100 that encloses the gas pipe 110, and the sample liquid is allowed to flow through the pipe 120 into the thermostatic container 100. The temperature of the water is made to coincide with the temperature of the water before being supplied to the gas pipe 110.

  In the above configuration, the sample liquid is allowed to flow from the lower side of the gas pipe 110 while flowing the sample liquid to the gas pipe 110 along the pipe wall from the upper side in the drawing. Is detected as a voltage of the gas sensor 130. The gas concentration of the alcohol that is included in an equilibrium state at the current temperature (measurement temperature) is detected. Based on the voltage thus detected, the alcohol concentration in the sample solution is calculated.

  Here, as the temperature of the sample liquid, for example, the temperature at which the gas sensor has the highest sensitivity is selected, and the relationship between the concentration of alcohol in the carrier gas and the concentration in the sample liquid in a state where the temperature is fixed in this way is previously determined. In other words, when the gas concentration is determined, the concentration of alcohol in the sample solution is determined.

  In FIG. 6, the pipe 120 is branched in order to measure other elements of the sample solution.

  Japanese Patent Laid-Open No. 05-045263 discloses an alcohol concentration measurement device using bubbling. The relationship between the current temperature (measurement temperature) of the sample and the temperature set in the thermostatic chamber is a problem in the following. Is not mentioned at all.

Japanese Patent Laid-Open No. 05-045263

  The measurement of the alcohol concentration by the above configuration requires water strictly controlled at a predetermined temperature by a thermostat and a carrier gas maintained at the same temperature as the water, and the apparatus becomes large and the cost increases. I must. In addition, since the measurement work is performed on the assumption that the temperature of the sample solution is maintained at a predetermined temperature with water from the thermostatic chamber and that the temperature of the carrier gas is also maintained at the same temperature, there is some cause. If the temperature of the water in the thermostat and the temperature of the sample solution or the temperature of the carrier gas are different, a measurement error will occur.

  On the other hand, the gas concentration of alcohol in the carrier gas varies greatly depending on a slight temperature difference. As a result, when temperature control during measurement is not strictly maintained, the above measurement error becomes extremely large.

  If the measurement temperature, gas concentration, and the three-dimensional relationship between the concentration are stored in the storage means as an equation or a table and the concentration is directly derived from the gas concentration obtained from the measurement temperature, the temperature in the thermostatic chamber The theory that management becomes unnecessary and the desired concentration can be easily obtained is established as a desk theory, but the data becomes enormous and the cost demerit is large and not suitable for practical use.

  The present invention has been proposed in view of the above-described conventional circumstances, and can accurately measure the gas concentration of the target substance without strictly managing the temperature of the sample liquid and the temperature of the carrier gas, As a result, an object of the present invention is to provide a gas concentration measuring device and a gas concentration measuring method capable of measuring the concentration of a target substance in a sample solution.

  In order to achieve the above object, the present invention employs the following means.

First, the temperature of the sample liquid containing the measurement target substance and the gas concentration of the measurement target substance contained in the carrier gas bubbled or contacted with the sample liquid are detected. From the relationship between the temperature at a specific concentration of the measurement target substance in the sample liquid and the gas concentration, the gas concentration in the carrier gas of the measurement target substance at the temperature of the sample liquid is converted to the gas concentration at the target temperature. Next, the concentration of the measurement target substance in the sample solution is obtained from the gas concentration at the target temperature.

  The above method is realized by the following apparatus.

A container filled with a sample solution containing a substance to be measured and a lid that seals the opening at the upper end of the container are provided, and a thermostatic block protrudes from the lid into the container. A vent hole is provided through the lid and the thermostatic block so that a carrier gas is bubbled through the vent hole in the sample solution. The measurement hole passes through the lid, communicates the inside and outside of the container, and discharges the bubbled carrier gas to the outside. A gas sensor is provided in a measurement hole that penetrates the lid and communicates the inside and outside of the container, and detects a gas concentration of a measurement target substance contained in the bubbled carrier gas . Further, the temperature of the sample liquid filled in the container is measured by the temperature sensor. In the temperature correction means, the gas concentration obtained from the gas sensor at the temperature of the sample solution obtained by the temperature sensor is determined at the target temperature from the relationship between the temperature and the gas concentration at a specific concentration of the measurement target substance in the sample solution . The gas concentration is converted (corrected), and the calculation means calculates the concentration of the substance to be measured in the sample liquid from the gas concentration at the target temperature.

  Here, temperature control means is provided in the thermostatic block, the sample liquid is thermostatically controlled by the thermostatic block, and the carrier gas is bubbled into the sample liquid through the vent hole penetrating the thermostatic block. The carrier gas is held at the same temperature close to the target temperature.

The gas concentration at the temperature of the sample solution obtained by the temperature sensor is corrected to the gas concentration at the target temperature, and the corresponding concentration is obtained from the gas concentration at the target temperature. For the conversion from the gas concentration at the target temperature to the corresponding concentration, a known relational expression or table is used, or a dedicated expression is created and used. Therefore, even if the temperature of the sample solution is different from the target temperature, the concentration based on the gas concentration corrected to the target temperature is always calculated, so that relatively accurate and quick measurement can be performed.

FIG. 1 is a conceptual diagram showing a densitometer of the present invention. FIG. 2 is a graph showing the relationship between temperature and gas concentration at a specific concentration. FIG. 3 shows an example in which the alcohol concentration is measured using the densitometer of the present invention. FIG. 4 shows an example of measuring the alcohol concentration using the densitometer of the present invention. FIG. 5 shows an example in which the alcohol concentration is measured using the densitometer of the present invention. FIG. 6 is a conceptual diagram showing the prior art.

FIG. 1 is a diagram showing an embodiment of the present invention. The case where the target substance for concentration measurement in the sample solution is alcohol will be described as an example. The opening at the upper end of the container 10 containing the sample solution (for example, beer) is sealed by the lid 11. A thermostatic block 12 made of a material having a high thermal conductivity such as metal protrudes from the lower surface of the lid 11 into the container 10, and a vent hole 13 for introducing a carrier gas into the lid 11 and the thermostatic block 12 is provided. It penetrates and the inside and outside of the container communicate with each other.

  Further, the carrier gas introduced into the container 10 is discharged to the outside from the measurement hole 15 penetrating the inside and the outside of the container 10 through the lid body 11. 16 is provided, and the gas concentration of alcohol contained in the sample solution is detected as a voltage.

  A temperature sensor 21 is provided for detecting the temperature of a sample solution containing a substance to be measured (alcohol) in the container 10. Furthermore, the temperature block 12 is also provided with a temperature sensor 22, and the temperature of the temperature block 12 is set to a target temperature (described later) via a thermal element (heating or cooling means, for example, a heater) 23 embedded in the temperature block. Alternatively, the temperature control means 20 controls the temperature close to that. At the same time, the temperature of the sample solution immersed in the constant temperature block 12 and the carrier gas introduced from the vent hole 13 are also maintained at a target temperature (described later) or a temperature close thereto.

  Further, an arithmetic unit 30 that calculates the alcohol concentration of the sample using the output of the gas sensor 16 is provided and operates in response to the output of the sample liquid temperature sensor 21 and the gas sensor 16. The operation is as follows. It will be described together with the measurement procedure.

  First, a sample liquid such as beer to be measured is filled in the container 10, and air as a carrier gas is injected from the vent hole 13 at a predetermined speed. As a result, the carrier gas is bubbled into the sample solution and released from the measurement hole 15 to the outside. When the carrier gas passes through the sample liquid, it is balanced with the concentration of the sample liquid and the concentration of the alcohol gas corresponding to the temperature, and the gas concentration is measured by the gas sensor 16 provided in the measurement hole 15 and detected as a voltage.

  At this time, the temperature of the constant temperature block 12 is detected by the thermometer 22, and as described above, the thermal element 23 is controlled by the temperature control means 20 so that the temperature becomes the target temperature or a value close to the target temperature. As a result, the temperature of the sample solution and the temperature of the carrier gas passing through the vent hole 13 are also controlled to the target temperature or a value close to the target temperature.

  With the above configuration, a carrier gas in which alcohol vapor is balanced at the current temperature (measurement temperature) is obtained and passes through the measurement hole 15, so that a voltage corresponding to the gas concentration Pts can be obtained from the gas sensor 16. Become. This value is input to the temperature correction means 31 of the arithmetic unit 30. The output of the temperature sensor 21 for measuring the sample liquid temperature (measurement temperature Ts) is also input to the temperature correction means 31.

  The storage means built in the temperature correction means 31 stores the relationship between the temperature of the alcohol solution having a specific concentration and the gas concentration as shown in FIG. 2 as an equation or a table. Here, a concentration close to the alcohol concentration to be obtained (for example, 5 vol% for beer) is selected as the specific concentration.

  The temperature correction means 31 of the arithmetic unit 30 obtains the ratio Pts / Pto = Rs between the gas concentration Pts at the measured temperature Ts and the gas concentration Pto at the target temperature To input as described above from the above equation or table. Here, the temperature (for example, around 35 ° C.) with the highest sensitivity of the gas sensor 16 is selected as the target temperature To.

  Since this ratio may be considered to be almost the same as the “ratio of the gas concentration at the measurement temperature Ts to the target temperature To at the alcohol concentration to be determined”, the output Vs of the gas sensor 16 at the measurement temperature Ts is the target. It is converted into the output Vo at the temperature To by the following formula.

(Equation 1)
Vo = Vs / Rs = Vs / (Pts / Pto) (1)
According to the calculation of the above equation (1), the voltage Vo corresponding to the alcohol gas concentration of the sample liquid at the target temperature can be obtained even if the sample liquid does not reach the target temperature.

  The voltage Vo obtained as described above is input to the concentration calculating means 32. The storage means built in the concentration calculation means 32 stores the relationship between the gas concentration at the target temperature To and the alcohol concentration in the sample solution as an equation or a table. When the voltage Vo is input, the corresponding concentration is stored. It has come to be obtained.

  3 to 5 show the results of measuring a sample solution having an alcohol concentration of 6 vol% using the concentration measuring apparatus of the present invention. In the figure, (a) is a sample temperature curve (right scale), (b) is a concentration obtained without temperature correction, and (c) is a concentration obtained by the present invention.

  As shown in FIG. 3 above, when the temperature of the sample solution is greatly changed and the temperature correction is not performed (curve (b)), the concentration obtained with the temperature change also changes greatly. The measurement result in the invention (curve (c)) does not reflect the effect of temperature change, and shows a value close to the original concentration even when the difference between the sample liquid temperature and the target temperature (35 ° C) is relatively large. ing.

  The phenomenon shown in FIG. 3 is caused when the sample liquid temperature is brought close to the target temperature while slowly changing as shown in FIG. 4, or the sample liquid temperature is forcibly brought close to the target temperature as shown in FIG. The same applies to the case. That is, in the present invention (curve (c)), the original concentration is obtained even if the measured temperature is different from the target temperature, but when temperature correction is not performed (curve (b)), the target temperature and The difference between the two becomes prominent as a density error.

  Although only the concentration meter shown in FIG. 1 has been described above, the present invention can also be applied to the conventional alcohol concentration meter shown in FIG. That is, the output of the gas sensor 16 of FIG. 1 is equivalent to the output of the gas sensor 130 shown in FIG. 6, and the output of the gas sensor 130 is input to the temperature correction means 31 of the arithmetic unit 30 of FIG. Even if the temperature does not exactly match the target temperature, the temperature can be corrected and the concentration calculation means 32 can obtain a highly accurate concentration.

  In the above description, alcohol is used as an example, but it goes without saying that any volatile substance can be used as the target substance.

  As described above, the present invention can accurately measure the concentration of a volatile substance even if the measurement temperature is not exactly the target temperature, and has a very simple configuration, so that it can be used industrially. Extremely expensive.

DESCRIPTION OF SYMBOLS 10 Container 11 Cover 12 Constant temperature block 13 Ventilation hole 15 Measurement hole 16 Gas sensor 20 Temperature control means 21 Temperature sensor 22 Thermometer 30 Arithmetic device 31 Temperature correction means 32 Concentration calculation means

Claims (4)

A container filled with a sample solution containing a substance to be measured;
A lid for sealing the opening of the container top end,
A thermostatic block protruding into the container from the lid;
A ventilation hole provided through the lid and the thermostatic block, for bubbling a carrier gas into the sample liquid;
A gas sensor that is provided in a measurement hole that penetrates the lid and communicates the inside and outside of the container, and that detects a gas concentration of a measurement target substance contained in the bubbled carrier gas ;
A temperature sensor for measuring the temperature of the sample liquid filled in the container;
The gas concentration obtained from the gas sensor at the temperature of the sample solution obtained by the temperature sensor is converted into the gas concentration at the target temperature from the relationship between the temperature and the gas concentration at a specific concentration of the substance to be measured in the sample solution. Temperature correction means;
Calculating means for the gas concentration, it calculates the concentration of the sample solution of target substance in the target temperature,
A densitometer characterized by comprising: The densitometer according to claim 1, further comprising temperature control means for controlling the block temperature near the target temperature in order to keep the temperature of the sample solution and the temperature of the carrier gas near the target temperature . Using the thermometer according to claim 1,
With measuring the temperature of a sample solution containing a target substance which is filled in a container, comprising the steps of detecting the gas concentration of the target substance that contains said carrier gas is bubbled into the sample solution,
Converting the detected gas concentration at the temperature of the sample liquid to the gas concentration at the target temperature from the relationship between the temperature and gas concentration at a specific concentration of the substance to be measured in the sample liquid;
Calculating the concentration of the substance to be measured in the sample liquid from the gas concentration at the target temperature;
A concentration measuring method comprising: Detecting the temperature of the sample solution containing the analyte, the gas concentration of the analyte contained in the carrier gas that is bubbled or contact with the sample solution,
A step of converting the gas concentration in the carrier gas of the measurement target substance at the temperature of the sample liquid into the gas concentration at the target temperature from the relationship between the temperature at the specific concentration of the measurement target substance in the sample liquid and the gas concentration. And
Obtaining the concentration of the substance to be measured in the sample liquid from the gas concentration at the target temperature ;
A concentration measuring method comprising:

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